MathDB
Putnam 2007 A4

Source:

December 3, 2007
Putnamalgebrapolynomiallogarithmsquadraticscollege contests

Problem Statement

A repunit is a positive integer whose digits in base 10 10 are all ones. Find all polynomials f f with real coefficients such that if n n is a repunit, then so is f(n). f(n).